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Electrical Brain Stimulation to Treat Neurological Disorders
Published in Bahman Zohuri, Patrick J. McDaniel, Electrical Brain Stimulation for the Treatment of Neurological Disorders, 2019
Bahman Zohuri, Patrick J. McDaniel
The most recent player to the electrical stimulation field is transcranial Random Noise Stimulation (tRNS). This method, akin to adding “white noise” to ongoing neural activity, is thought to open ion channels at the neuron.29 In one of the first studies in normal human subjects, stimulation over the motor cortex (between 100 and 640 Hz for 10 minutes at 1.5 mAmp) was found to increase cortical excitability.30 These authors hypothesize that, like tACS, tRNS “can possibly interfere with ongoing oscillations and neuronal activity in the brain and thus result in a cortical excitability increase.” There are several potential advantages of tRNS over tDCS: while tDCS can open ion channels once, tRNS can do so repeatedly through multiple ionic influxes;tRNS works around problems associated with stimulation of different sides of a folded cortex which can lead to effects which cancel each other out;tRNS does not create a “tingling” sensation, as does tDCS when applied;safety concerns are minimized. A recent study found superior performance of high frequency (100–640 Hz) tRNS over tDCS (1.5 mAmp) in normal subjects on a perceptual learning task.11
A touching story
Published in Journal of Neurogenetics, 2020
Working with John was fun (as was enjoying a beer with him at the pub at the Frank Lee Centre near the lab). He approached research with a straight-forward understanding and clarity that I always envied. And he always came up with unique ways of solving problems. At one point, we did a series of experiments to show that the TRNs were, indeed, the touch-sensing cells. John, using the laser microscope developed by John White, would kill the TRNs in different combinations, confirm that the affected cell nuclei were missing, blind the samples, and give them to me to test for touch sensitivity. The experiments went very smoothly until one day when John and I disagreed about one of the animals. I said it was touch sensitive in the tail and he said it could not be because it lacked both tail TRNs. After a considerable amount of discussion, we both retested the animal for touch sensitivity and John reexamined it under the Nomarski microscope. We agreed that the animal was touch sensitive, but surprisingly, it seemed to lack both cells. We were puzzled, but John was determined to find an answer. He asked Nichol Thomson to do an electron microscopic ‘autopsy’ on the worm. Nichol took pictures of the worm at different positions along the animal’s length and found that one TRN neurite was, indeed, still there. Apparently, the laser ablations had killed one cell but had only destroyed the nucleus in the other. The enucleated cell, however, appeared to function perfectly well.
Dimensions of Ethical Direct-to-Consumer Neurotechnologies
Published in AJOB Neuroscience, 2019
Consider, for example, neurostimulation devices, such as Startstim neurostimulation, which is advertised as performing transcranial direct current stimulation (tDCS), transcranial alternative current stimulation (tACS), transcranial random noise stimulation (tRNS), with the aim of enhancing, among other things, executive functions, language, attention, learning, memory, mental arithmetic, and social cognition (Startstim 2018). If such DTC neurotechnology is indeed an effective intervention that can be used to gain a benefit in a competitive environment, such as in school or the workplace, justice demands that it not be the exclusive asset of the wealthy but be equitably shared amongst members of society (see similar arguments regarding pharmacological enhancement (Maslen, Faulmüller, and Savulescu 2014)).
Improvement of gait and balance by non-invasive brain stimulation: its use in rehabilitation
Published in Expert Review of Neurotherapeutics, 2019
tDCS involves applying small (approx. 1–2 mA) direct currents to the scalp with pad electrodes. The outcome is determined by the placement of the anodal and cathodal stimulation pads [27]. Newer methods of transcranial electrical stimulation include transcranial alternating current stimulation (tACS), transcranial random noise stimulation (tRNS) and oscillating tDCS (otDCS) [28]. During standard tDCS using two pad electrodes, the direction of current flow differentially modulates the resting membrane potential of the neurons stimulated [27]. Anodal stimulation depolarizes the neurons, increasing the probability of action potentials occurring, whereas cathodal stimulation hyperpolarizes neurons, thus decreasing the likelihood of action potentials occurring [12]. Current flow may be affected by electrode impedance (quality of skin contact), head size, scalp and skull thickness and cortical surface topography [9]. More recently high-density tDCS (HD-tDCS) using ‘ring electrodes’ has been introduced. These electrodes consist of five small electrodes, such as a single anode surrounded by four cathodes or vice versa. This 4 × 1 ring montage has been shown to enhance spatial focality [29].